In recent years, in order to improve the fuel economy of an automotive internal combustion engine, studies are being conducted on techniques related to lean burn control (lean burn engines) or EGR which returns combustion gas to the cylinder of the internal combustion engine. In these techniques, various ignition systems for effectively burning the fuel included in the air-fuel mixture have been proposed, such as the multiple ignition scheme in which the ignition plug generates discharge a plurality of times consecutively at the ignition timing of the internal combustion engine, and the DCO scheme in which the ignition plug generates discharge continuously for a fixed period of time which is close to the ignition timing. In these ignition devices, for example, when a short failure or an open failure occurs in the ignition coil, it becomes difficult for the spark plug to generate a spark discharge.
The ignition device that performs multiple ignition described in PTL 1 comprises a capacitor, and the electric energy stored in the capacitor is supplied to the ignition coil by turning on a switching means called a second switching means. A large secondary current flows through the secondary coil due to the inrush current at this time, and spark discharge is generated at the spark plug. Then, the switching means is turned off, a large secondary current flows through the secondary coil, and spark discharge is generated at the spark plug. It is described that, according to such an ignition device, any failure in the ignition device can be monitored by reading the current flowing through the switching means.